Detection systems for the railroad industry provide methods and apparatus for detecting dragging, or otherwise improperly hanging or protruding vehicle equipment or objects when a train passes by a monitoring station. Existing systems for detecting dragging equipment underneath trains include sensors mounted on stationary strike plates or impact elements in the path of the protruding equipment. Impacts of protruding equipment against the stationary impact elements cause vibrations in the impact elements and in the sensors mounted thereon. Systems or apparatus for detecting the presence of objects dragging beneath a train are sometimes referred to as “draggers”. In various implementations, draggers are placed at twenty mile intervals, ten mile intervals, or other spaced intervals along stretches of railroad track, in addition to being placed at railroad crossings and in railroad switching yards. If a dragging object, or otherwise improperly protruding equipment, is detected by a dragger, the train is stopped so that the object can be secured or removed to reduce the potential for derailment or other problems. Because of the expense and inconvenience of stopping a train frequently to secure low-risk objects, a system and method is needed for accurately detecting and characterizing dragging objects under a variety of conditions and train speeds so that the train will only be stopped when absolutely necessary to prevent derailment.
One problem associated with existing impact detection systems involves the triggering of false alarms. In some situations, false alarms can be triggered because the impact detection system does not adjust or compensate for different conditions under which detection of impacts is being performed, and therefore does not provide an accurate characterization of the impact. A failure to accurately identify or characterize the type of detected impact can occur if the sensors used to detect the impacts are not able to adjust or compensate for the range of conditions that affect the magnitude of impact forces. A sensor may be expected to accurately detect impact forces generated by equipment being dragged by a train traveling at a variety of speeds, from very slowly at speeds of 1-20 miles per hour, to fast speeds in excess of 60 miles per hour.
One attempt to avoid the problem of triggering false alarms is disclosed in U.S. Pat. No. 6,412,332 to M. Bartonek that issued on Jul. 2, 2002 (the '332 patent). The '332 patent discloses an apparatus for detecting objects dragging beneath a train as the train travels along a rail. The apparatus includes a stationary impact element rigidly supported along the rail, with a single axis sensor disposed in a horizontal orientation relative to the impact element to detect only horizontal components of any impact forces.
Although the impact detection system of the '332 patent may eliminate detection of vertical forces, and therefore reduce the detection of vibrations from flat wheels, this solution for selective detection of only impacts that create horizontal forces may provide a less than optimal impact detection system. In particular, the impact detection system of the '332 patent does not adjust for different conditions under which detection of impacts is being performed.
The disclosed dragging equipment detector is directed to overcoming one or more of the problems set forth above and/or other problems in the art.